One widely used process for the generation of electricity entails the use of a fuel-fired turbine to turn a generator. The turbine turns by the introducing a hot exhaust gas through the turbine. In this process, catalysts have been used for igniting and burning the combustible fuel. The fuel and an oxygen-containing gas, typically air, are mixed and introduced into a combustion apparatus containing the catalysts. The mixture is burned over the catalysts and the resulting high temperature exhaust gas is introduced into the turbine. The efficiency of the generation process is largely dependent upon the temperature of the gas introduced into the turbine. That is to say, the higher the temperature of the burned gas, the higher the efficiency of the turbine at least so long as the turbine's materials are able to withstand the high temperatures. A typically appropriate temperature range for modern gas turbines is between 1300.degree. C. and 1500.degree. C.
Although it is desirable to introduce all of the needed fuel and oxygen-containing gas needed to reach a desired exhaust gas temperature into the catalyst, it is quite difficult to control the temperature within that catalyst.
At present, we do not know of any catalyst which is capable of operating at the desired turbine gas temperature of 1300.degree. C. or above for an appreciable period of time without substantial deterioration of the catalyst. Others have suggested that controlling catalyst temperatures at a level at which catalyst deterioration is minimized may be accomplished by introducing the needed fuel into the catalyst in a series of stages rather than introducing all of the fuel together. This approach obviously requires the separation of the catalyst bed into a series of separate beds in which the temperature rise in each is separately controlled.
However, even this suggested process does not possess the ability consistently to produce an exhaust gas at a temperature over 1300 .degree. C. since the catalyst in the latter stages must face that temperature and consequently will deteriorate. Additionally, since the fuel is introduced into the catalyst at a number of points, the apparatus surrounding the catalyst is complex and its operation is complicated. Exhaust gases containing up to 10 ppm NO.sub.x or more may be produced because the fuel in the final stage is likely imperfectly or nonuniformly mixed with the partially combusted gases from the earlier stages.
In contrast, however, the present invention does not cause the temperature of the exhaust gas in the catalyst structure does not rise to a level which will cause the catalyst to undergo deterioration. The gas will be at a temperature, however, that will allow homogeneous combustion of uncombusted fuel to occur after the partially combusted gas leaves the catalyst bed. In other words, the resulting gas is ultimately produced at a temperature which is at or above the deterioration temperature of the catalyst without deteriorating the catalyst.
Additional fuel and air need not be supplied to the intermediate stages of the of the catalyst since all of the fuel needed to produce the desired exhaust temperature is supplied initially to the catalyst. No fuel concentration gradient in the catalyst bed is needed to suppress NO.sub.x production. Finally the complicated apparatus needed to supply fuel to the various catalyst stages of that known process is not needed.